Purification Methods
Purify it by ion exchange on Amberlite IRC-150 and eluting with 0.1-4M HCl. [Stolowitz & Minch J Am Chem Soc 103 6015 1981.] It has been isolated as the tri-reineckate salt by adding 2volumes of 1% solution of ammonium reineckate in 2% perchloric acid. The reineckate salt separates at once but is kept at 2o overnight. The salt is collected on a sintered glass funnel, washed with 0.5% of ammonium reineckate, dried (all operations at 2o) and stored at 2o. To obtain adenosylmethionine, the reineckate is dissolved in a small volume of methyl ethyl ketone (MEK) and centrifuged at room temperature to remove a small amount of solid. The clear dark red supernatant is extracted (in a separating funnel) with a slight excess of 0.1N H2SO4. The aqueous phase is re-extracted with fresh MEK until it is colourless. [Note that reineckates have UV absorption at 305nm ( 15,000), and the optical density at 305nm is used to detect and estimate reineckate ions.] MEK is removed from the aqueous layer containing adenosylmethionine sulfate; the pH is adjusted to 5.6-6.0 and extracted with two volumes of Et2O. The sulfate is obtained by evaporating the aqueous layer in vacuo. The hydrochloride can be obtained in the same way but using HCl instead of H2SO4. SAM-HCl has a solubility of 10% in H2O. The salts are stable in the cold at pH 4-6 but decompose in alkaline media. [Cantoni Biochemical Preparations 5 58 1957.] The purity of SAM can be determined by paper chromatography [Cantoni J Biol Chem 204 403 1953, Methods Enzymol 3 601 1957], electrophoretic methods or enzymic analysis [Cantoni & Vignos J Biol Chem 209 647 1954]. [Beilstein 26 III/IV 3676.]
